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In the present study, the magnetic domains and their evolution during magnetization process have been investigated for sintered Nd-Fe-B permanent magnets with Kerr microscopy. Observation of the magnetic domain evolution process during magnetization process shows that some domain walls were pinned at the grain boundary area under magnetic field up to 5 kOe. It is suggested that magnetic interaction between individual Nd2Fe14B grains contacting to each other leads to appearance of small closed domains near the grain boundary area, which are responsible for the pinning effect. [ABSTRACT FROM AUTHOR]

Ce-Fe-B rare-earth alloys are alternative to substitute partially for Nd-Fe-B permanent magnets for reducing the cost and the balance use of rare-earth elements. However, coercivity is rather low in Ce-Fe-B magnets, which partially ascribes to the instability of Ce 2 Fe 14 B phase and the low magnetocrystalline anisotropy. In this paper, magnetic properties are investigated in Ce 13-x Gd x Fe 81 B 6 ribbons via substituting of Gd for Ce. X-ray diffraction shows that a little amount of Gd substitution for Ce leads to an increase in the intensity of diffraction peak for main phase, which should be attributed to the improvement of the stability of R 2 Fe 14 B phase and the reduction in the amount of amorphous phase. Even though the magnetocrystalline anisotropy is lower in Gd 2 Fe 14 B than that in Ce 2 Fe 14 B, the coercivity increases to 5.88 kOe for a little amount of Gd substitution in Ce 12 Gd 1 Fe 81 B 6 ribbons. For Gd atomic percent more than 3% the coercivity decreases, and the remanence drops significantly. With the increase of Gd atomic percent, Curie temperature increases monotonically. Henkel plots indicate that Gd substitution for Ce could enhance the effect of exchange coupling, which owes to the increase of exchange coefficient in main phase as well as to the reduction in the amount of amorphous phase. These investigations show that a little amount substitution of Gd is beneficial to improve the magnetic properties without a significant drop of the remanence. [ABSTRACT FROM AUTHOR]

(Ce,Nd)-Fe-B sintered magnets were prepared by the addition of NdH x powders in Ce 9 Nd 4.5 Fe 80 B 6.5 powders. The coercivity is rather low in Ce 9 Nd 4.5 Fe 80 B 6.5 magnets, and Ce element prefers to distribute at the outer-layer of main phase (Ce,Nd) 2 Fe 14 B. The investigation of scanning electron microscope shows that the addition of NdH x powders leads to the increase of Nd content at grain outer-layer of main phase owing to the element diffusion. Magnetization reversal undergoes the nucleation of reversed domain wall at grain outer-later, and the addition of NdH x powders leads to the increase in the nucleation field of reversed domain, giving rise to the significant improvement of coercivity. The larger amount addition of NdH x powders leads to the increase in the amount of intergranular phase, resulting in the decreases of the remanence, the squareness of demagnetization curve and the maximum energy product. [ABSTRACT FROM AUTHOR]

High energy ball milling (HEBM) is employed to produce nano-sized grains and particles. In this paper, the structure and magnetic properties are investigated in PrCo5 alloy for HEBM in an ethanol milling medium. With the increase of milling time, the grain size reduces and the coercivity increases. For a milling time of less than 30 min, the hysteresis loop of the aligned sample is very different from that of the un-aligned sample and it does not show a large decrease in magnetization slope, indicating a relatively good alignment of easy axes in particles due to the fact that the texture is nearly well preserved. However, when the milling time is further prolonged, the textured structure deteriorates in the powders. Even though exchange coupling exists between grains within the particle, the magnetic properties are exchange-decoupled between particles and the dipolar interaction results in a negative value of δm in the whole range of the magnetic field. [ABSTRACT FROM AUTHOR]